Typical end closures for beer and beverage containers have an opening panel and an attached tab for pushing the opening panel into the container to open the end. The container is typically a drawn and ironed metal can, usually constructed from a thin plate of aluminum. End closures for such containers are also typically constructed from a cutedge of thin plate of aluminum or steel, formed into a blank end, and manufactured into a finished end by a process often referred to as end conversion.
These types of container ends have been used for many years, with almost all such ends in use today being the “ecology” or “stay-on-tab” (“SOT”) ends in which the tab remains attached to the end, including large-opening ends (“LOE”), after a tear panel is opened. The tear panel being a portion of the can end defined by a frangible score length and a non-frangible hinge segment. The tear panel may be opened, that is the score may be severed, and the tear panel displaced at an angular orientation relative to the remaining portion of the can end, thus creating a pour opening through which the beverage may be poured from the container. The tear panel remains connected by the non-frangible hinge segment to the remaining portion of the can end by the non-frangible hinge segment, leaving an opening through which the user draws the contents of the container. In an LOE, the pour opening is about 0.5 square inches (3.23 cm2) in area.
Opening of the tear panel is operated by the tab which is attached to the can end by a rivet through a rivet island on the tab. The tab is typically attached to the can end such that a nose of the tab extends over a proximal portion of the tear panel in a stowage position. A lift end of the tab is located opposite the tab nose and provides access for a user to lift the lift end, such as with the user's finger, to force the nose against the proximal portion of the tear panel. With most can ends, the stowage position and opening position are in the same location; however, some can ends known in the art require rotation of the tab from a stowage position to the opening position prior to an opening sequence, i.e. the fracturing of the frangible score.
When the tab nose is forced against the tear panel, the score initially ruptures at a vent region of the score. This initial rupture of the score is primarily caused by the lifting force on the tab resulting in lifting of a central region of the can end, including the rivet and immediately adjacent the rivet. As the tab is lifted further, the score rupture propagates along the length of the score, eventually stopping at the hinge segment.
Venting is an initial release of pressure from within a pressurized container upon initial fracture of the score about the tear panel, typically upon the initial lifting of the lift end of the tab by a user.
In general, beverage can end design requires a careful balancing of structural elements to achieve a beverage can end of a desired strength while maintaining proper function of the SOT opening assembly. Changes to one structural element to improve one physical characteristic of the beverage can end will routinely adversely affect a different physical characteristic.
Frangible score geometry plays a large role in the openability of such a beverage can end. It is desirable for the frangible score to fracture properly and for the fracture to propagate about the tear panel from one end of the frangible score to the other. Manufacturers often seek to alter frangible score geometry to enlarge the tear panel opening to improve pourability; however, often when pourability is improved, the design change or score geometry change may adversely affect openability.
Thus, the problem addressed by the inventors can be stated: in a beverage can end or lid comprising a stay-on-tab ecology opening assembly, what is alternative tear panel geometry that produces a suitable pour opening area and shape and that opens in a manner where the fracture of the frangible score propagates from a first end adjacent the rivet about a curvilinear path to a second end wherein the first end and the second end are separated by a non-frangible hinge segment of the center panel. One goal of the present invention to increase or improve pourability without sacrificing openability.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior can ends of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.